Electrospray Ionisation (ESI)
Definition
A soft atmospheric-pressure ionisation source that sprays the LC eluent through a charged capillary into a heated counter-current gas, producing protonated or deprotonated molecular ions of polar and ionic analytes with little fragmentation. John Fenn shared the 2002 Nobel for chemistry for the work that made ESI a routine bench technique.
- Type
- Soft atmospheric-pressure ionisation source
- Primary use
- LC-MS (liquid chromatography-mass spectrometry)
- Best for
- Polar and ionic analytes, drugs, peptides, metabolites
Common questions
What is ESI and how does it work in LC-MS?+
Electrospray ionisation is a soft atmospheric-pressure ionisation method that sprays the liquid chromatography eluent through a charged capillary into a heated counter-current gas. This produces charged droplets that become protonated or deprotonated molecular ions with little fragmentation, making it ideal for detecting polar and ionic compounds.
Why is ESI useful for forensic analysis of drugs and metabolites?+
ESI generates intact molecular ions for peptides, drugs, and conjugated metabolites. Because it is a soft ionisation technique, molecules experience little fragmentation, preserving the parent ion and making it easier to identify compounds of interest in forensic samples.
Who developed ESI and how significant was it?+
John Fenn shared the 2002 Nobel Prize in Chemistry for the work that made ESI a routine bench technique, showing how transformative it has been for analytical science.
Related terms
- Atmospheric Pressure Chemical Ionisation (APCI)
- A complementary atmospheric-pressure source that vaporises the LC eluent and uses a corona discharge to ionise a reagent gas, which transfers charge...
- GC-MS Interface
- The physical link between a gas chromatograph and a mass spectrometer. Older designs used jet separators and open splits to manage the...
- Hyphenated Technique
- A single workflow that couples a separation method to a spectroscopic detector, so a complex mixture is resolved and each component identified...
- Hyphenation
- Online coupling of a separation technique (GC, LC, ICP) with a spectrometric detector (MS, FTIR) so identification happens within the same run....
- ICP Plasma
- Inductively coupled argon plasma at 6,000 to 10,000 K that atomises and ionises samples in ICP-MS, generating singly charged elemental ions for...
- Interface
- The hardware bridge that transfers analyte from the separation stage to the detector while removing the unwanted mobile phase (carrier gas, solvent,...
- Internal Standard / Deuterated Standard
- A chemically similar (often perdeuterated) compound spiked into the sample to correct for matrix effects and ionisation suppression. Standard practice in forensic...
- Isotope Ratio Mass Spectrometry (IRMS)
- Specialised MS that measures precise ratios of light stable isotopes (delta values of 2H, 13C, 15N, 18O, 34S) on a continuous-flow combustion...
- Jet Separator
- Early GC-MS interface (Ryhage, 1964) that used differential pumping through a nozzle to enrich analyte and bleed helium. Replaced by direct capillary...
- MRM (Multiple Reaction Monitoring)
- A targeted MS/MS scan mode on a triple quadrupole that monitors specific precursor-to-product ion transitions, with two transitions per analyte (quantifier and...
- Vapour-Phase IR Spectrum
- The infrared spectrum recorded as a GC analyte elutes into a heated light pipe inside the FTIR cell, with no solvent or...
Explained in these topics
- Hyphenated Techniques: GC-MS, LC-MS and GC-FTIRA soft atmospheric-pressure ionisation source that sprays the LC eluent through a charged capillary into a heated counter-current gas, producing protonated or...
- Hyphenated Techniques in Forensic Science: GC-MS, LC-MS, IR-MS and ICP-MSSoft atmospheric-pressure ionisation used in LC-MS. Generates charged droplets from the eluent, gives intact molecular ions for peptides, drugs and conjugated...